In the photoengraving step in the field of photographic printing and duplication, a method is generally employed in which a photographic image having continuous gradation is converted into a so-called dot image, expressing the light and shade of the image in accordance with the size of various dot areas constituting the image. The dot image is combined with a letter image, a line image to give a printing plate.
The silver halide photographic material used in this method must have so-called ultra-hard photographic characteristics with a high contrast and a high blacking density, clearly distinguishing the image area from the non-image area. These characteristics result in good reproducibility of clearly reproducing letters, line images and dot images.
To attain this purpose, a method for forming a photographic image having a high contrast and a high blacking density has heretofore been employed In that method, the photographic material with a silver chlorobromide emulsion (i.e., one having a silver chloride content of 50 mol% or more) is processed with a hydroquinone developer (lith developer) having an extremely low effective sulfite ion concentration (generally, 0.1 mol% or less). Silver halide photographic materials of the kind are known as lith photographic materials.
However, since a lith developer, having a low sulfite ion concentration, easily undergoes aerial oxidation and its preservability is extremely poor, it is used in continuous operation with various techniques and devices for the purpose of keeping a constant developed quality.
A method for rapidly forming a high contrast image with a processing solution having a good storage stability, while overcoming the instability of the image formed by lith development, has been proposed in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,875, 4,224,401, 4,243,739, 4,272,606, 4,311,781 and 4,650,746. The new method is characterized by processing a surface latent image type silver halide photographic material containing a particular hydrazine derivative compound with a superadditive developer containing a sulfite preservative in a high concentration and having a pH value of from 11.0 to 12.3.
In accordance with the new development system, elevation of the stability of the developer used has been made possible by incorporation of a sulfite preservative in a high concentration thereinto. However, in order to obtain a high contrast image by this method, a developer having a pH value higher than that of a conventional lith developer or a rapid access developer is required. Since the pH value of the developer is high, it can not be said to have sufficient stability even though it contains a sulfite preservative of a high concentration. Accordingly, there has been a strong demand for lowering the pH value of the developer.
U.S. Pat. No. 4,269,929 and JP-A-61-267759 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") describe a method for forming a high contrast photographic image with a developer having a lower pH value, in which an amine compound capable of promoting the contrast-elevating activity of hydrazines is added to the developer.
On the other hand, JP-A-60-179734, JP-A-61-170733, JP-A-61-270744, JP-A-62-948, JP-A-63-234244 and JP-A-2-00747 and U.S. Pat. No. 4,798,780 describe various hydrazine derivatives having a high contrast-elevating activity, in which various efforts to elevate the stability i development have been made.